/**
 * Session persistence. Sessions REQUIRE byte-exact persistence: the relay
 * validates against the exact granted object, and any re-serialization that
 * reorders keys or reformats values breaks the session. These helpers are
 * the only supported way to write a session to disk or read one back.
 *
 * bigint fields (spend limits) are encoded as "bigint:<decimal>" strings,
 * the same convention the spike session files on disk already use.
 */

import { deserializeSession, serializeSession } from './codec';

export { deserializeSession, roundTripIsExact, serializeSession } from './codec';

// File helpers stay in this Node-only module. Browser consumers import the
// separate `@agripinaa/session-kit/codec` entrypoint instead.

export async function saveSessionFile(path: string, session: unknown): Promise<void> {
  const { chmod, mkdir, rename, unlink, writeFile } = await import('node:fs/promises');
  const { dirname } = await import('node:path');
  const dir = dirname(path);
  await mkdir(dir, { recursive: true, mode: 0o700 });
  await chmod(dir, 0o700);
  const temporary = `${path}.${process.pid}-${Date.now()}.tmp`;
  try {
    await writeFile(temporary, serializeSession(session), { encoding: 'utf8', flag: 'wx', mode: 0o600 });
    await chmod(temporary, 0o600);
    await rename(temporary, path);
    await chmod(path, 0o600);
  } catch (error) {
    await unlink(temporary).catch(() => {});
    throw error;
  }
}

export async function loadSessionFile(path: string): Promise<unknown> {
  const { readFile } = await import('node:fs/promises');
  return deserializeSession(await readFile(path, 'utf8'));
}